diff --git a/runtime/lua/vim/filetype.lua b/runtime/lua/vim/filetype.lua
index ac8ff2a1e3..8266125f6b 100644
--- a/runtime/lua/vim/filetype.lua
+++ b/runtime/lua/vim/filetype.lua
@@ -444,6 +444,8 @@ local extension = {
   rej = 'diff',
   dj = 'djot',
   djot = 'djot',
+  Containerfile = 'dockerfile',
+  containerfile = 'dockerfile',
   Dockerfile = 'dockerfile',
   dockerfile = 'dockerfile',
   bat = 'dosbatch',
diff --git a/test/old/testdir/test_filetype.vim b/test/old/testdir/test_filetype.vim
index 37c539c53f..79d6b62492 100644
--- a/test/old/testdir/test_filetype.vim
+++ b/test/old/testdir/test_filetype.vim
@@ -246,7 +246,7 @@ func s:GetFilenameChecks() abort
     \ 'dircolors': ['.dir_colors', '.dircolors', '/etc/DIR_COLORS', 'any/etc/DIR_COLORS'],
     \ 'djot': ['file.dj', 'file.djot'],
     \ 'dnsmasq': ['/etc/dnsmasq.conf', '/etc/dnsmasq.d/file', 'any/etc/dnsmasq.conf', 'any/etc/dnsmasq.d/file'],
-    \ 'dockerfile': ['Containerfile', 'Dockerfile', 'dockerfile', 'file.Dockerfile', 'file.dockerfile', 'Dockerfile.debian', 'Containerfile.something'],
+    \ 'dockerfile': ['Containerfile', 'Dockerfile', 'dockerfile', 'file.Dockerfile', 'file.dockerfile', 'file.Containerfile', 'file.containerfile', 'Dockerfile.debian', 'Containerfile.something'],
     \ 'dosbatch': ['file.bat'],
     \ 'dosini': ['/etc/yum.conf', '/etc/nfs.conf', '/etc/nfsmount.conf', 'file.ini',
     \            'npmrc', '.npmrc', 'php.ini', 'php.ini-5', 'php.ini-file', 'php-fpm.conf', 'php-fpm.conf.default', 'www.conf', 'www.conf.default',